Fewer than 3% of adult U.S. cancer patients are estimated to participate in NCI- sponsored clinical research trials. Trial closure due to inadequate accrual presents a frequent, costly deterrent to advancing cancer care and has been recognized as an essential priority on the national level. Previous research has focused on barriers to accrual occurring after a trial opens;comprehending accrual problems by focusing on processes occurring before a trial opens presents a novel research approach. The objective of this study is to improve clinical trial design and prioritization by performing the first systematic evaluation of the combined clinical trial accrual experience of five national cooperative oncology trial groups. We hypothesize that the process of trial design and prioritization will be improved by (1) developing a predictive model for trial accrual success, (2) evaluating the impact of trial redesign efforts on accrual, and (3) establishing accrual benchmarks below which trials should strongly be considered at high failure risk. The specific aims of this project are (1) to identify factors predictive of clinical trial accrual success in the cooperative trial group setting in order to improve phase III clinical trial design and prioritization;(2) to demonstrate the influence of trial redesign methods on clinical trial accrual success;and (3) to develop and validate evidence-based benchmarks for clinical trial termination or redesign. Data for this study will be obtained both through data abstraction of existing source documents at the individual cooperative groups and through a survey of clinical trial study chairs and lead statisticians from the cooperative trial groups. Importantly, a consensus regarding the trial features to be examined and their standardized definitions will be achieved by the investigators with representatives from each cooperative group comprising the Advisory Panel prior to initiating data collection.